Up to now, for example, an antenna device for a milliwave radar detecting a target by using an electromagnetic wave in the milliwave band is disclosed in Patent Document 1 (Japanese Unexamined Patent Application Publication No. 11-127001). In the antenna device shown in this Patent Document 1, a plurality of primary radiators is time-division switched by using dielectric lines and dielectric line switches, and transmission-reception wave beams are scanned such that the position of effective primary radiators is moved in the focus plane of a dielectric lens.
The antenna device shown in Patent Document 1 has the advantage of having a relatively simple structure and performing beam scanning by simple actions. However, in the antenna device shown in Patent Document 1, since beam scanning is performed by mechanical displacement of the position of the primary radiators, there are problems in that it is difficult to increase the speed of beam scanning beyond a certain level, that power consumption needed for the beam scanning is relatively large, and that operation noise is caused when beam scanning is performed. In addition, since the position of the primary radiators is mechanically displaced, it can be assumed that the life is limited by the wear of sliding portions and the reliability is low when compared with other electronic components.
Furthermore, since the positional displacement of the plurality of primary radiators always has the same pattern, it is impossible to direct the beam in a desired direction and randomly scan beam directions even if required.
Furthermore, since only the relative position of the primary radiators to the lens is displaced, it is impossible to change the radiation pattern of beams.
It is an object of the present invention to provide an antenna device in which the above-described problems are solved, the beam scanning is speeded, power consumption for the beam scanning is reduced, operation noise in the beam scanning is eliminated, the reliability is improved, and, when required, the beam direction can be directed to any direction.
Furthermore, it is another object of the present invention to provide an antenna device in which the above problems are solved and, when required, the radiation pattern of beams can be changed.